Post-Construction Stormwater Management

What is Post-Construction Stormwater Management?

Post-Construction Stormwater Management refers to the activities that take place after construction occurs, and includes structural and non-structural controls to obtain permanent stormwater management over the life of the property's use.

Why Is The Control of Post-Construction Runoff Necessary?

Post-construction stormwater management in areas undergoing new development or redevelopment is necessary because runoff from these areas has been shown to significantly affect receiving water bodies. Many studies indicate that prior planning and design for the minimization of pollutants in post-construction stormwater discharges is the most cost-effective approach to stormwater quality management.

There are generally two forms of substantial impacts of post-construction runoff. The first is caused by an increase in the type and quantity of pollutants in stormwater runoff. As runoff flows over areas altered by development, it picks up harmful sediment and chemicals such as oil and grease, pesticides, heavy metals, and nutrients (e.g., nitrogen and phosphorus). These pollutants often become suspended in runoff and are carried to receiving waters, such as lakes, ponds, and streams. Once deposited, these pollutants can enter the food chain through small aquatic life, eventually entering the tissues of fish and humans.
The second kind of post-construction runoff impact occurs by increasing the quantity of water delivered to the water body during storms. Increased impervious surfaces (e.g., parking lots, driveways, and rooftops) interrupt the natural cycle of gradual percolation of water through vegetation and soil. Instead, water is collected from surfaces such as asphalt and concrete and routed to drainage systems where large volumes of runoff quickly flow to the nearest receiving water. The effects of this process include stream bank scouring and downstream flooding, which often lead to a loss of aquatic life and damage to property.

What Bowling Green is Doing

BG City Ordinance (21-2.05) requires post-construction best management practices (BMPs) to be emplaced for any land disturbance over one acre and includes more than 10,000 square feet of impervious cover. Alone or together, BMPs for any development meeting the threshold must reduce total suspended solids by 80%.

Development

Bowling Green has sustained a steady growth rate for within the last ten years. The 2000 Census determined the population of Bowling Green to be 49,600. Given this growth and impacts from growth, several regulations are in-place to minimize impacts from development. Development must consider quantity and quality aspects of Stormwater from the site.

Underground Injection Control Program

Bowling Green has historically utilized dry wells as a means of drainage when conventional methods are not possible. This program is regulated as a Class V injection well by the EPA, the designation is given based on a non-hazardous influent that does not meet the criteria of the other classes. Class V wells must be reported to the EPA as well as the City of Bowling Green.

Bowling Green is utilizing best management practices (BMPs) from the Phase II permit to minimize pollutants into the injection well or dry well. The usage of this type of drainage, karst, is valuable to Bowling Green, and it is an asset which needs to be preserved and protected. The replacement of karst drainage would be extremely difficult and costly.